E4440A振幅读数很低

大家好，我有一个PSA E4440A似乎有一个问题，用预选器纠正。
这会影响3GHz以上的所有输入。
例如，我输入5GHz @ -10dBm。
无论我的跨度设置如何，我都可以看出振幅读数很低，约为-35dBm。
我将频率居中，并将跨度减小到20MHz。
标记读数为5.000000，幅度为-35dBm。
如果我点击Presel中心，信号会跳到-10到-11之间。
右侧菜单上的Presel Adjust显示47.80MHz，之前读取0Hz。
每次改变频率时我都要经历这个例行程序。
从我在手册中阅读的内容和论坛上看，可能会出现1或2dB的偏移，而不是我得到的25dB。
我错了。
我有两个仪器正在执行此操作，第三个正常运行，在击中Presel Center之前振幅非常接近，按下它后变化不大。
所以我的问题是，如果有人知道这是一个关闭的设置，可能在工厂预设中丢失的校准常数，可以通过TME软件调整修复的调整，还是硬件故障？
谢谢，迈克



     以下为原文

  Hi everyone,

I have a PSA E4440A that appears to have a problem that is corrected with the preselector. This affects all inputs over 3GHz. As an example, I input 5GHz @ -10dBm. Regardless of what I have the span set to, I can tell that the amplitude is reading low, around -35dBm. I center the frequency, and reduce the span to 20MHz. The marker reads 5.000000, with an amplitude of -35dBm.
If I hit the Presel Center, the signal jumps up to between -10 and -11 where it should be. The Presel Adjust on the right side menu shows 47.80MHz, where as before it read 0Hz.  
I have to go through this routine every time I change frequency.  
From what I read in the manual, and here on the forum, 1 or 2dB of shift might be expected, not the 25dB that I’m getting. I could be wrong.

I have two instruments that are doing this, and a 3rd that acts as normal, the amplitude is pretty close before hitting the Presel Center, and doesn’t change much after pressing it. So my question is if anyone knows whether this is a setting that got switched off, cal constants that might have been lost in a factory preset, an adjustment that can be fixed with a TME software adjustment, or if it is a hardware fault?

Thanks,
Mike